The adjustment of the sliding rails to other bolt diameters in conventional devices of the aforementioned type is time-consuming and requires special skill from the machine setter. The exchanging of the sliding rail end sections, which are wear-prone parts, is likewise cumbersome since these are threaded in place by means of several screws.
A feeding device for rod-shaped workpieces, especially welding electrodes, has been known from DE-AS 1,272,823. This apparatus comprises a vertical guide chute below a funnel-shaped storage container, this chute being defined by walls or rails, the mutual spacing of which is adjustable in adaptation to the diameter of the rods (welding electrodes) by way of oblique fishplates forming a parallelogram. The walls of the guide chute are swung to and fro by way of an eccentric and a bar for separating the rods and depositing them on a conveyor belt.
In a feeding device for eyelet rings and the like in riveting machines known from DE-AS 2,151,081, a sliding rail gap is adjusted by way of an adjusting spindle and oblique slots in order to adapt the gap to the diameter of the workpieces.